Vacuum kneading method with the introduction of oxygen and the device used to carry out said method

ABSTRACT

The invention relates to a method of kneading dough in order to produce bread or similar products. According to the invention, the dough ingredients are introduced into a chamber and all of said ingredients are subsequently kneaded. The inventive method is characterised in that it comprises: a vacuum phase during which a vacuum is applied in the chamber; and one or more phases involving the introduction of gas, during which a gas containing oxygen is introduced into the chamber. The aforementioned vacuum phase continues more or less throughout the entire kneading phase, with at least one part of each introduction phase taking place simultaneously with the kneading phase. The invention also relates to a device that is used to carry out said method.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a National Phase Application of PCT/FR02/03542,which claims priority to French Patent Application No. 0113521, filedOct. 19, 2001, entitled “Vacuum Kneading Method with the Introduction ofOxygen and the Device Used to Carry Out Said Method,” both of which areincorporated by reference herein.

BACKGROUND OF THE INVENTION

The invention concerns a method of kneading dough for making bread orsimilar products and a device for implementing the said method.

The document EP-A-0 246 768 describes a method and apparatus forkneading bread dough in an oxygen-enriched atmosphere. To this end,oxygen or oxygen-enriched air is introduced into the chamber of theapparatus contained in the dough before or during kneading. Theatmosphere in the chamber is then discharged through a discharge pipe.This addition of oxygen promotes the action of the ascorbic acid, usedas a single improving product (known as an improver in the technicalfield).

This document describes that the application of a partial vacuum in thechamber is not necessary but that it can be implemented before theintroduction of the oxygen or the oxygen-enriched air.

However, this method does not make it possible to control thedevelopment of the bubble structure in the bread dough.

According to the document EP-A-0 629 115, it is known that theproduction of a partial vacuum during kneading improves the uniformityof the structure of the soft part of the bread. However, the creation ofa partial vacuum removes the air, which reduces the oxidation of theimprovers used by bakers (ascorbic acid or potassium bromate) forintensifying the formation of the gluten lattice and, stabilising thestructure of the bubbles.

The document EP-A-0 629 115 describes a dough kneading method foroptimising the use of ascorbic acid as an improver. To this end, themethod comprises the kneading of the dough ingredients in the presenceof air or a gas containing oxygen. During a first phase of thiskneading, an overpressure is applied to the atmosphere surrounding thedough, whilst a reduced pressure is applied during a second phase of thekneading. The first phase allows oxidation of the ascorbic acid, thesecond phase controlling the structure of the bubbles in the dough.

This method has the drawback of requiring two kneading phases, includingone phase under air overpressure which is difficult to achieve withnormal kneading means.

This is because high forces are exerted by the air pressure on themixing chamber and on its mechanical environment such as for example themixing tool or tools, the sealing joint or joints, and the lid of thevessel.

SUMMARY AND OBJECTS OF THE INVENTION

The invention aims to resolve the aforementioned drawbacks of the priorart by proposing a method affording adequate oxygenation of the dough atthe same time as controlling the structure of the bubbles within it.

The method thus optimises the uniformity of the structure of the softpart of the bread whilst guaranteeing sufficient oxygenation thereof.

To this end, a first object of the invention is a method of kneadingdough for making bread or similar products, in which the ingredients ofthe dough are introduced into a chamber, and then the said ingredientsare kneaded together, characterised in that it comprises:

-   -   a negative-pressure phase during which a negative pressure is        applied in the chamber (2);    -   a phase or several phases of introducing gas G during which a        gas G containing oxygen is introduced into the chamber (2);        the negative-pressure phase lasting for substantially the entire        duration of the kneading phase, at least part of each        introduction phase being simultaneous with the kneading phase.

No overpressure with respect to atmospheric pressure is thus applied inthe chamber, which avoids the application of stresses. In a variant, thenegative-pressure phase begins just a little time before or after thestart of the kneading phase and/or finishes just a little time before orafter the end of the kneading phase.

In another variant, the gas introduction phase or phases begin just alittle time before or after the start or end of the kneading phase,and/or finish just a little time before or after the start or end of thekneading phase.

In one embodiment, the method comprises a single phase of introducingthe gas G which lasts substantially throughout the kneading phase.

In another embodiment, the method comprises several introduction phases,the intervals of time between these phases and the duration of each ofthese phases being variable.

Each introduction phase can last from a few seconds to several tens ofminutes.

Moreover, during each introduction phase, it is possible to vary theflow rate of gas G.

And during the negative-pressure phase, it is possible to apply anabsolute pressure in the chamber (2) of between 0.02 bar and 0.98 bar.

In a variant, the gas said (G) can be introduced into the chamber (2) inthe volume of the dough (P).

A second object of the invention is a device implementing the methoddescribed above.

This device comprises a chamber formed by a vessel intended to containthe dough and a removable lid hermetically closing the said vessel, andkneading means comprising a rotor.

The said device is characterised in that it comprises gas supply meansopening out in the chamber and pipes for discharging the atmosphere fromthe chamber opening out in the chamber at a distance from the dough.

In a variant, the said supply means and the said discharge pipes aredisposed on substantially opposite parts of the chamber.

In one embodiment, the said discharge pipes are connected to at leastone vacuum pump.

In another embodiment, the said feed means open out in the bottom partof the said chamber.

The gas then passes through the dough before being discharged, formingair bubbles therein. The dimensions of these air bubbles are veryrapidly reduced by virtue of keeping the chamber under partial vacuum.

In a first embodiment of the device, the axis of the rotor of the saiddevice is horizontal and the fixing and sealed guidance of the rotorwith respect to the said vessel are achieved by means of two bearings,each bearing comprising in particular

-   -   a bearing body comprising means of fixing to the vessel, and        having a central recess or seat for the end part of the rotor to        pass;    -   sealing means arranged for providing the dynamic sealing of the        chamber;    -   a jacket in the form of a substantially cylindrical part of        revolution, fitted on the said end part of the rotor and        interposed between it and the bearing body, the sealing means        being disposed between the seat of the bearing body and the        jacket.

The means of supplying gas to the vessel are then situated at the meansof sealing the said bearing.

This configuration makes it possible to use means already existing forthe introduction of the gas.

In a variant, the said bearing sealing means comprise a plurality of lipjoints fitted in a housing of the seat, the lips of the jointscooperating with a first end part of the jacket turned towards thevessel, at least one of the joints being oriented so that its lip isturned towards the vessel, whilst at least one of the other joints isoriented so that its lip is turned in the opposite direction.

In this variant, the gas supply means open out in the housing betweenthe vessel and the said joint whose lip is turned towards the vessel.

In another variant, the said bearing sealing means comprise a pluralityof lip joints fitted in a housing of the seat, the lips of the jointcooperating with a first end part of the jacket turned towards thevessel, two juxtaposed joints being oriented so that the lip is turnedtowards the vessel whilst at least one of the other joints is orientedso that its lip is turned in the opposite direction.

In this variant, the gas supply means open out in the housing betweenthe said juxtaposed joints whose lip is turned towards the vessel.

The gas arriving under overpressure then raises the joint disposedbetween the supply means and the vessel. In addition, the passage of thegas between the two joints prevents the dough from being introduced intothis space, guaranteeing the hygiene of the latter.

In a second embodiment of the device the axis of the rotor of the deviceis horizontal and the vessel is asymmetric with respect to a verticalplane P passing through the rotation axis of the rotor.

The vessel comprises a first substantially vertical side wall, and asecond side wall inclined by a given angle to the vertical. The curvedvessel bottom connects the first wall to the second side wall, so thatthe vessel comprises, on the side of the second side wall, a spacewidening out towards the top in the form of a crescent, situated betweenthe second side wall and the path followed by the free end of the rotorblades.

In this embodiment, the gas supply means open out in the said space.

Thus the supply means open out outside the passage of the rotor bladesand are easily accessible.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects and advantages of the invention will emerge during thefollowing description of embodiments, with reference to the accompanyingdrawings, given by way of non-limiting examples, in which:

FIG. 1 is a schematic representation of a device implementing thekneading method of the invention;

FIG. 2 is a view in axial section of a first embodiment of the device inFIG. 1, said device comprising a vessel and a rotor rotatably fixed onthe vessel by two sealed roller bearings;

FIG. 3 is an enlarged view of the sealing means of the sealed bearingsof the device in FIG. 2;

FIG. 4 is a variant of the sealing means depicted in FIG. 3;

FIG. 5 is a view in axial section of a second embodiment of the devicein FIG. 1;

FIG. 6 is a diagram representing the starting of the rotor as a functionof time during the kneading phase;

FIG. 7 is a diagram representing possible profiles of the negativepressure in the chamber as a function of time and;

FIG. 8 is a diagram depicting possible profiles of the gas flow as afunction of time.

The X-axes of the diagrams depicted in FIGS. 6 to 8 coincide so as to beable to compare the durations of the various kneading, negative pressureand introduction phases of the method.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 depicts schematically a kneading device 1, comprising a chamber 2formed by a vessel 3 intended to contain the dough P and a removable lid4, hermetically closing the said vessel 3, and providing its staticsealing.

The said device 1 also comprises kneading means 5 comprising a rotor 6.

The rotation axis X of the rotor 6 can be either vertical or horizontal.The horizontalness being defined with respect to the floor on which thedevice 1 is resting, the vessel 3 being able to be fixed or tilting.

In the embodiments in FIGS. 2 to 5, the axis X of the rotor 6 ishorizontal.

The rotor 6 is mounted for rotation in the vessel 3 and is actuated by amotor 7.

Supply means 8 open out in the chamber 2 and for example in the vessel 3to allow the introduction of a gas G containing oxygen into the saidvessel.

In one embodiment, the supply means 8 open out in the bottom part of thevessel 3, in the volume of the dough P, so that the gas G passes throughthe dough P.

These supply means 8 are for example nozzles or openings situated on thevessel 3 and connected to one or more reservoirs 9 of gas G. It is alsopossible to use, as gas supply means 8, means of supplying water to thesaid chamber 2.

A regulation valve 10 can also be provided for regulating the flow ofgas G in the supply means 8.

It is thus possible to regulate the flow of gas G, in particularaccording to the nature and quantity of dough, the volume of the vesseland the required result.

One or more flow meters 11 can be used for measuring the flow of gas Gintroduced by the supply means 8 into the chamber 2.

The device 1 also comprises one or more pipes 12 for discharging theatmosphere present in the chamber 2. These pipes 12 open out in thechamber 2 at a distance from the dough P. They can be situated on thelid 4 or on the top part of the vessel 3, above the dough P.

These discharge pipes 12 are connected to at least one vacuum pump 13,which provides a partial vacuum in the chamber 2. The atmosphere in thechamber is thus under negative pressure with respect to the atmosphericpressure outside the chamber and with respect to the pressure in thesupply means 8.

Pressure measurement means, such as pressure gauges, can be used formeasuring the pressures in the supply means 8 and in the chamber 2.

The functioning of the vacuum pump or pumps 13 is adjusted so that nooverpressure with respect to atmospheric pressure is applied in thechamber 2.

Thus the gas G is introduced into the chamber 2 through the supply means8 and is then sucked into the discharge pipes 12 by the vacuum pump orpumps 13. A circulation of gas is thus caused in the chamber 2. Thiscirculation is represented by the arrows F in the figures.

The gas supply means 8 and the discharge pipes 12 can be disposed onsubstantially opposite parts of the chamber 2 in order to help the gas Gto pass through the dough P.

The pressure in the chamber 2 is such that it is lower than the pressurein the supply means 8 and/or the reservoir 9.

A pressure difference is thus created in the chamber 2 and the reservoir9 of gas G, assisting the introduction of the gas G into the chamber 2.

The pressure difference can be accentuated by increasing the gaspressure in the reservoir 9 and/or in the supply pipes 8.

Particular embodiments of the device 1 and of the supply means 8 are nowdescribed in detail.

In a first embodiment, with reference to FIGS. 2 to 4, the axis X of therotor 6 is horizontal and the fixing and sealed guidance of the rotor 6with respect to the said vessel 3 are achieved by means of bearings 14.

One of the bearings 14 is now described in detail, assuming the twobearings to be identical.

The bearing 14 comprises a bearing body 15 which has a through centralrecess 16 called a seat, having symmetry of revolution, and in which anend part 17 of the rotor 6 is inserted.

The bearing body 15 is fixed to a side wall of the vessel 3 on theexternal side, by means of removable fixing means 18 such as screwsregularly distributed over the circumference of the bearing body 15.

The bearing body 15 is fixed in line with an opening 19 formed in thesaid side wall of the vessel 3, so that the axis of revolution of theseat 16 coincides with the rotation axis X of the rotor 6.

The bearing 14 is designed to provide a total seal of the inside of thevessel 3 with respect to the ambient atmosphere outside it.

To this end, the bearing 14 comprises dynamic sealing means 20comprising a plurality of lip joints 21, 22, 23 mounted in series andfitted in a part of the seat 16 called a housing 24, adjacent to theopening 19 formed in the side wall of the vessel 3.

In the embodiment illustrated in FIG. 3, three lip joints 21, 22, 23 areprovided, between a shoulder 25 of the housing 24 and an internalcirclip 26 inserted in a groove formed in the housing 24.

The joints 21, 22, 23 are arranged both to provide the dynamic seal forthe vessel 3 and to maintain it under pressure, the pressure inside thevessel being able to be lower than atmospheric pressure, for example 50millibars, whilst the speed of rotation of the rotor in operation isgenerally between 10 revolutions per minute and 250 revolutions perminute.

To this end, at least one 21 of the joints, for example the one closestto the vessel 3, is oriented so that its lip is turned towards theinside of the vessel 3, whilst at least one 23 of the others is orientedso that its lip is turned towards the outside of the vessel.

Means 8 of supplying gas G to the vessel 3 are situated at the sealingmeans 20 of the said bearing 14.

To this end a bore is provided in the bearing body 15 in order tointroduce the gas G.

This bore opens out on the one hand in the housing 24 of the sealingmeans 20 and on the other hand outside the bearing, on a part of theexternal surface of the bearing which is not in contact with anotherpiece.

In the first variant in FIG. 3, the lips of the joints 21, 22 cooperatewith the end part 17 of the jacket 32 turned towards the vessel 3, thetwo joints 21, 22 being oriented so that their lip is turned towards thevessel 3, whilst the other joint 23 is oriented so that its lip isturned in the opposite direction.

In this variant, the means 8 of supplying the gas open out in thehousing 24, between the juxtaposed joints 21, 22.

The difference in pressure between the chamber 2 and the supply means 8thus assist the raising of the lip of the joint 21 and the passage ofthe gas G to the chamber.

In the second variant in FIG. 4, only two juxtaposed joints 22, 23 areused, the two joints 22, 23 being oriented so that their lip is turnedrespectively towards the vessel 3 and in the opposite direction.

The gas supply means 8 then open out in the housing 24 between thevessel 3 and the said juxtaposed joints 22, 23.

These supply means 8 can be disposed on the two bearings 14 of therotor, or on one of the two. It is also possible to envisage theproduction of one or more bores in a bearing 14 for introducing the gasG.

The gas is thus introduced as close as possible to the dough, directlyon the rotor.

One embodiment of the structure of a bearing 14 is now described indetail with reference to FIG. 3.

In order to ensure rigid holding of the joints 21, 22, 23 in theirhousing 24 between the shoulder 25 and the circlip 26, at least onespacer 27 can be inserted between two successive joints 21, 22.

In addition, in order to provide the rotational guidance of the rotor 6,the bearing 14 comprises at least one roller bearing 28 interposedbetween the bearing body 15 and the end part 17 of the rotor 6.

The bearing 28 comprises a fixed external ring 29, associated with thebearing body 15 whilst for example being fitted in a bore 30 of the seat16, a movable internal ring 31, and bodies rolling on each other, suchas balls, needles or cylindrical or conical rollers.

The lip joints 21, 22, 23 and the bearing 28 are not in direct contactwith the end part 17 of the rotor 6.

This is because the bearing 14 comprises an intermediate piece 32 ofrevolution, substantially cylindrical and hollow, called a jacket,fitted on the end part 17 of the rotor 3 and interposed between the saidpart and the bearing body 15.

The jacket 32 has a first end part 33 turned towards the inside andinserted in the seat 16 of the bearing body 15, and a second oppositeend part 34, projecting from the seat 16 towards the outside.

The roller bearing 28 is interposed between the seat 16 of the bearingbody 15 and the jacket 32, its inner race 31 being fitted on the jacket32, and mounted clamped between a projecting shoulder 35 on the jacket32 and a nut 36 screwed on the threaded part 37 of the jacket 32.

In addition, the lip joints 21, 22, 23 are interposed between thebearing body 15 and the jacket 32, their lips being in contact with thefirst end part 33 of the jacket 32.

In addition, in order on the one hand to provide the clamping of theoutlet race 29 of the bearing 28 and on the other hand to ensure acomplementary seal on the bearing 14, the latter comprises a cover 38associated with the bearing body 15.

To this end the cover 38 comprises a cover body 39 in the form of a partof revolution having a central recess 40 for passage of the end part 17of the rotor 6 and of the second end part 34 of the jacket 32 fittedthereon.

The cover 38 also comprises removable means 41 of fixing the cover body39 to the bearing body 15, on the opposite side to the vessel 3, that isto say on the side turned towards the outside.

These fixing means 41 are for example in the form of a plurality ofscrews regularly distributed over the circumference of the cover body38.

In addition, the cover comprises a lip joint 42 interposed between thecover body 39 and the jacket 32.

The lip joint 42 is for example fitted in a housing 43 provided in thecentral recess 40 of the cover body 39, its lip being in contact withthe second end part 34 of the jacket 32.

In addition, the jacket 32 has an end 43 projecting from the cover 38towards the outside.

In order to connect together, at least with respect to rotation, thejacket 32 and the end part 17 of the rotor 6, the bearing comprises anannular clamping collar 44 enclosing the end 43 of the jacket 32, thiscollar forming a means for the removable fixing of the jacket 32 to therotor 6.

In a second embodiment, with reference to FIG. 5, the device is suchthat the axis X of the rotor 6 is horizontal and the vessel 3 isasymmetric with respect to a vertical plane P1 passing through therotation axis X of the rotor.

The vessel comprises a first substantially vertical side wall 45 and asecond side wall 46 inclined by a given angle to the vertical.

The curved vessel bottom connects the first wall 45 to the second sidewall 46, so that the vessel 3 comprises, on the same side as the secondside wall 46, a space 47 opening out towards the top in the form of acrescent.

This space 47 is situated between the second side wall 46 and the pathfollowed by the free end of the rotor 6 blades. This path is representedby the curve C in FIG. 5.

The gas supply means 8 open out in the said space 47, outside thepassage area of the rotor 6 blades, and are thus easily accessible.

A particular arrangement of the walls 45, 46 of the vessel 3 isdescribed below.

The internal face 48 of the first side wall 45 comprises a verticalrectilinear portion 49 and a curved portion 50, connected at a junction51. The junction 51 belongs substantially to a horizontal plane P2passing through the axis X of the rotor 6. Thus the path C of the bladesis substantially tangent to the internal face 48, in fact separated by aspace e, substantially from the junction 51 over approximately ¼ of aturn as far as the bottom vertex S1 of the path C. The circular path Cmatching the shape of the internal face 48, the portion 49 is tangent tothe vertex S2 of the path C.

The internal face 48 of the second side wall 46 comprises a rectilinearportion 52 and a curved portion 53, connected at a junction 54.

Along the second side wall 46, the distance between the tangent to thepath C at the vertex S_(n) and the intersection I_(n) between the secondwall 46 and the radius R1 of the path passing through the intersectionI_(n) is defined as d_(n).

On the same side as the second side wall 46:

-   -   the portion 52 is inclined by an angle β of around 10° to the        vertical;    -   the intersection I_(n) is separated from the vertex S_(n) by the        distance d_(n).

Thus the plane P2 intersects the second side wall 46 at the intersectionI1, the vertex Sn is marked with the reference 55, the intersection I1and the vertex 55 are spaced apart by the distance d1.

An angle δ is defined between on the one hand the vertical plane P1passing through the axis of the rotor 6 and on the other hand a plane P3passing through the axis of the rotor 6 and the junction 54 between theportion 52 and the portion 53. The best results obtained correspond to avalue of δ of around 100°.

It is possible to use a device comprising a vessel 3 as described in thesecond embodiment and where the fixing and sealed guidance of the rotor6 with respect to the said vessel 3 are achieved by means of bearings 14described in the first embodiment.

The supply means 8 described in these embodiments can then be used incombination or alone.

The dough kneading method is now described.

During a first step, the lid 4 is opened so as to allow the introductionof the ingredients of the dough P into the chamber 2.

These ingredients comprise in particular flour, water and other elementsused in baking. Amongst the latter, ascorbic acid can be used as animprover. However, good results are obtained with the method of theinvention without using ascorbic acid.

The ingredients are then introduced into the chamber and the lid 4 isclosed again hermetically in order to ensure that the chamber 2 issealed.

The rotor 6 is then started up so as to stir the ingredients of thedough P. The functioning of the rotor corresponds to the kneading phase.

The method also comprises:

-   -   a negative-pressure phase during which a pressure below        atmospheric pressure is applied in the chamber 2,    -   one or more phases of introducing the gas G containing oxygen        during which the gas G is introduced into the chamber 2.

The negative-pressure and introduction phases help to create acirculation of gas in the chamber 2.

The negative-pressure phase lasts substantially throughout the kneadingphase.

It can begin just a short time before or after the start of the kneadingphase and end just a short time before or after the end of the kneadingphase.

Several introduction phases can be applied during the kneading phase.The intervals of time between these phases and the duration of each ofthese phases can be variable.

Each of these introduction phases takes place substantially during thekneading phase. A phase can however begin or end just a little timebefore or after the start or end of the kneading phase.

Thus at least part of each introduction phase and the kneading phase aresimultaneous.

A kneading phase lasting from a few minutes to several tens of minutes,each phase of introducing the gas G can last from around a few secondsto several tens of minutes. Thus a phase can last substantiallythroughout the kneading only for a short time during the kneading.

The introduction of the gas G for a period less than the kneading timeis implemented to the detriment of oxygenation but does however assistthe reduction of the structure of the alveoli in the soft part of thebread obtained.

During the introduction phase, the rate of introduction of the gas G canbe varied according to requirements. This rate can also vary from onephase to another during the same kneading phase.

During the negative-pressure phase, the negative pressure in the chamber2 is achieved by means of vacuum pumps 13 which function as long as thepressure in the chamber 2 is to be reduced.

In particular, in the absence of introduction of the gas G, thefunctioning of the vacuum pumps 13 can be suspended if the seal on thechamber is sufficient for a negative pressure to be maintained in thelatter.

During the negative-pressure phase, the absolute pressure applied in thesaid chamber 2 can be between 0.02 bar and 0.98 bar. It is possible tovary this pressure during the negative-pressure phase.

The number and duration of the gas introduction phases, as well as theduration of the negative-pressure phase and the value of the pressureapplied to the chamber during this phase, depend in particular on thenature and quantity of the dough P, the volume of the vessel and theresult required.

During the kneading, the speed of rotation of the rotor 6 can be variedin order to adapt it to the product required. The duration of thekneading phase is then in general longer and longer as the speed ofrotation of the rotor 6 is reduced.

At the end of the kneading phase, the functioning of the rotor 6 isstopped and, when the pressure in the chamber 2 is equal to theatmospheric pressure, the lid 4 is lifted off and the dough can beremoved.

In a variant of the method, during the phase of introduction of the gasG into the chamber 2, the gas G is introduced into the chamber 2 in thevolume of the dough P, so that the circulation of gas passes through thedough P.

In another variant, the gas G is introduced into the said chamber usingthe device for supplying water to the said chamber 2.

The gas containing oxygen can be air or any other gas containing oxygensuitable for producing the food dough.

Finally, control means can be provided for regulating the variousparameters of the method such as the pressure in the chamber and/or inthe supply pipes, the flow of gas G, the speed of rotation of the rotorand the duration of the various phases.

Examples of durations of the various phases are described below withreference to FIGS. 6 to 8.

FIG. 6 depicts the functioning of the rotor as a function of time, thecurve obtained representing the duration of the kneading phase.

FIG. 7 shows the pressure in the chamber 2 as a function of time. Thuscurves a, b represent examples of change in the pressure during thenegative-pressure phase.

Curve a (in a continuous line) corresponds to a phase during which thepressure in the chamber 2 is progressively reduced. The reduction in thepressure begins just a short time after the start of the kneading phaseand stops just a short time after the end of the kneading phase.

Curve b (in a broken line) corresponds to a rapid reduction in thepressure just a little time before the start of the kneading phase, thepressure increasing once again just a little time before the end of thekneading.

FIG. 8 depicts the flow of gas G introduced into the chamber 2 as afunction of time. Each curve c, d represents a phase of introducing thegas G.

Curve c (in a continuous line) corresponds to a single introductionphase during which the introduction of the gas commences just a littletime after the start of the kneading phase and ends just a little timeafter the end of the kneading phase. During this phase, the gas flowvaries as a function of time. Such a phase can for example be combinedwith the negative-pressure phase represented by curve a in FIG. 7.

Curve d (broken line) consists of three curves d1, d2 and d3corresponding to three introduction phases. During each of these phases,the gas is introduced at a constant rate, the rate varying from onephase to another. The durations and the intervals between these phasesare variable.

All these three phases, each of the phases, or all combinations betweentwo of these phases can be combined with the negative-pressure phaserepresented by curve b in FIG. 7.

An example of an implementation of the method is described below.

In this example, the device 1 described in the first embodiment is used.The volume of the vessel 3 is 400 liters.

The gas employed is air and the latter is introduced through the twobearings 14 of the rotor.

For 260 kg of bread dough, the following conditions are used forobtaining a good-quality bread dough:

-   -   duration of the kneading phase: 6 minutes 30 seconds;    -   at each bearing 14: introduction of air at a flow rate of 50        liters per minute and a pressure of 3 bar in the supply means 8;    -   pressure in the chamber 2: −0.8 bar, and the absolute pressure        in the chamber 2 is then 0.2 bar.

The phases of negative pressure and introduction of the gas G lastthroughout the kneading phase, the chamber being continuously maintainedunder negative pressure.

The method according to the invention can be applied to any kneadingdevice whose chamber can be put under partial vacuum. It then sufficesto add means of supplying gas to the said chamber.

1. A method of kneading dough for making bread or similar products, themethod comprising the steps of: introducing ingredients of the doughinto a chamber; kneading the ingredients together during a kneadingphase; applying a negative pressure during a negative-pressure phase inthe chamber, atmosphere present in the chamber being sucked above theingredients; and introducing gas which contains oxygen at flow rate ofapproximately 50 liters per minute or less during at least one gasintroduction phase into the chamber near a bottom portion thereof suchthat the gas passes through the ingredients; wherein a portion of thenegative-pressure phase is substantially simultaneous with the kneadingphase, the at least one gas introduction phase is substantiallysimultaneous with the kneading phase, and at least a portion of each gasintroduction phase is simultaneous with the negative-pressure phase. 2.A method according to claim 1, characterised in that the portion of thenegative-pressure phase begins near an end of the kneading phase.
 3. Amethod according to claim 1, characterised in that the at least one gasintroduction phase begins near the start or the end of the kneadingphase.
 4. A method according to claim 1, characterised in that the atleast one gas introduction phase finishes near the start or end of thekneading phase.
 5. A method according to claim 1, characterised in thatthe method comprises only one gas introduction phase, which lastssubstantially throughout the kneading phase.
 6. A method according toclaim 1, characterised in that the method comprises several gasintroduction phases, the intervals of time between the gas introductionphases and the duration of each of the gas introduction phases beingvariable.
 7. A method according to claim 1, characterised in that the atleast one gas introduction phase lasts from one second to sixty minutes.8. A method according to claim 1, characterised in that, during the atleast one gas introduction phase, the flow rate of the gas can bevaried.
 9. A method according to claim 1, characterised in that, duringthe negative-pressure phase, an absolute pressure in the chamber ofbetween 0.02 bar and 0.98 bar is applied.
 10. A method according toclaim 1, characterised in that the gas is introduced into the chamber asthe ingredients are kneaded together.
 11. A method according to claim 1,further comprising the step of oxidizing at least one of the ingredientsof the dough during the at least one gas introduction phase.
 12. Amethod of kneading dough for making bread or similar products, themethod comprising the steps of: introducing ingredients of the doughinto a chamber; providing an opening into the chamber; providing a rotorthrough the opening, the rotor adapted for kneading dough; providing atleast one bearing for the rotor adjacent to the opening; kneading theingredients together during a kneading phase with the rotor; applying anegative pressure during a negative-pressure phase in the chamber,atmosphere present in the chamber being sucked above the ingredients;providing a gas supply in the at least one bearing for the rotor; andintroducing gas which contains oxygen during at least one gasintroduction phase into the chamber near the opening such that the gaspasses through the ingredients; wherein a portion of thenegative-pressure phase is substantially simultaneous with the kneadingphase, and the at least one gas introduction phase is substantiallysimultaneous with the kneading phase.
 13. A method of kneading dough formaking bread or similar products, the method comprising the steps of:introducing ingredients of the dough into an asymmetric chamber;kneading the ingredients together during a kneading phase; applying anegative pressure during a negative-pressure phase in the asymmetricchamber, atmosphere present in the chamber being sucked above theingredients; and introducing gas which contains oxygen during at leastone gas introduction phase into the asymmetric chamber near a bottomportion thereof such that the gas passes though the ingredients; whereina portion of the negative-pressure phase is substantially simultaneouswith the kneading phase, and the at least one gas introduction phase issubstantially simultaneous with the kneading phase.